Means for mounting cups in mercury switches



y 31, 1951 E. v. TORGESON 2,562,752

MEANS FOR MOUNTING cuPs IQN MERCURY SWITCHES Original Filed Aug. 21, 1944 IN VEN TOR.

Everez f V To geson B Y ATTYS.

Patented July 31, 1951 MEANS FOR MOUNTING CUPS IN MEKCURY r SWITCHES Everett V. Torgeson, Elkhart, Ind., assignor to The Adlake Company, a corporation of Illinois Original application August .21, 1944, Serial No. 550,340. Divided and this application September 15,1949, Serial No. 117,827

4 Claims.

My invention pertains to mercury switches of the general type in which a displacement; means causes the mercury level to rise and fall relative to a mercury cup mounted on an electrode. Serious difliculties arise in designing such' a switch for carrying heavy current on the order of my to one hundred or more amperes. Only certain materials may be employed for fabricating the electrodes and mercury cups because the mercury environment precludes the use of most materials, because the arcing and generation of heat by the breaking of heavy duty circuits has a destructive effect on all but a few materials, and, finally, because the electrodes are usually restricted to materials having coefficients of expansion that match the coefiicient of expansion of adjacent sealing material.

The few materials that do qualify for use in electrodes and mercury'cups in high, amperage service are not easily assembled to make a switch construction satisfactory for prolonged service under high circuit loads. For example, molybdenum has the properties requiredfor an electrode and a quartz cup is superior in its ability to withstand the destructive effects of high amperage current but the nature of these materials is such that ordinary methods of mounting a mercury cup on an electrode do not result in a satisfactory and enduring construction.

It is essential that the quartz cup be permaently' mounted on the electrode with no signifi-' cant looseness and that the mounting be perma nent in spite of heat, vibration or shock.

Onemethod that has been tried for mounting a mercury cup on an electrode is to form an aper- It would seem that the possibility of short-- circuiting through failure of sealing material at the juncture of the electrode and mercury cup might be avoided by inserting the electrode into a recess in thewall of the mercury cup instead of into an aperture that breaks the continuity of the .cup wall, or might be avoided by causingthe electrode to engage astem or projection of the cup. The usual practices under such concepts are not successful for heavy duty switches, however, because permanence and sufficient rigidity in the cup mounting is not attained. If cement is used, it deteriorates, as heretofore stated, and usually results in a layer of insulating powder floating on the mercury fill, which powder may seriously interfere with the functioning of the switch. A simple glass bond fractures because of the great difierenential in rates of expansion at the joint. The use of a graded glass seal prohibited by the high cost.

Gne expedientheretofore suggested is the use of a special yielding or resilient fitting on the electrode to engage and retain a mercruy cup. It is not desirable, however, to introduce additional elements into compact switches and, furthermore, the particular fittings for this purpose of record in the art are not structurally efficient.

. Another concept of the method of mounting a mercury cup member on an electrode member is to preform one of the members with a suitable recess and to preform the other member to fit into the recess so closelyas to provide a rigid cup mounting by simple close-fitting mechanical interengagement of the two members with no necessity for any intervening bonding material. Quartz, however, is not a material suitable for preforming to the accuracy required under this concept, since quartz cannot be machined by any conventional procedure, and moreover, quartz, unlike ceramics, cannot be molded to close tolerances.

The general object of my invention is to provide a method of mounting a mercury cup, for example a quartz cup, on an electrode in a suf iciently tight manner that will be permanent under adverse conditions involving vibration or shock and will stand up under conditions of high amperage current. In general, this object is attained in the joining of a cup member to electrode member by inserting a portion of one of the two members in a recess in a portion of the other of the two members and then deform ing one of said portions to produce positiveand inseparable mechanical interengagements of the two members.

The term inseparable as used here and in my appended claims is to be taken as meaning that the parts are interlocked in such manner that separation may be accomplished only by fracturing or melting one of the members. It is contemplated that in most practices of the inven tion. mounting of the cup on the supporting electrode will involve encasing a portion of one of the members in a recess of the other member with a part of the encased portion enlarged and with the recess entrance restricted to prevent withdrawal of the enlargement.

The various practices of the present invention are characterized by the concept of deforming of material to produce the required mutual engagement after a portion of one member is inserted more or less loosely into a portion of the other member, as distinguished from the concept of accurately preforming both members to attain the required rigid mounting by merely moving the two members into mutual mechanical engagement. In my preferred practices, the electrode is preformed for the purpose of the inseparable engagement and heat is applied to deform portion of a quartz cup into the required interlocking relationship with the preformed electrode.

The above and other objects of my invention will be apparent in my following description, taken with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative,

Fig. 1 is a longitudinal sectional view of a mercury switch incorporating the preferred practice of my invention,

Fig. 2 is a fragmentary view partly in section indicating a stage in the manufacture of the switch at which the preformed electrode is moved into a preliminary relationship with a quartz cup, 7

Fig. 3 is a similar view indicating a later stage at which the quartz cup has been deformed by heat into permanent engagement with the electrode,

Fig. 4 is a view similar to Fig. 3 involving the use of a modified form of electrode,

Figs. 5 and 6 are similar to Figs. 2 and 3 to show another practice of the invention,

Figs. 7 and 8 are fragmentary sectional views disclosing another practice of the invention,

Figs. 9 and 10 are similar views indicating a further practice of the invention, and

Figs. 11 and 12 are similar views for a still further practice of the invention.

For the purpose of disclosure, I shall describe the various forms of my invention as incorporated in a mercuryswitch of the general type described in the patent to Larson, 2,266,469, entitled Mercury Switch Relay, issued December 16, 1941.

The embodiment of the invention shown in Fig. 1 includes a cylindrical switch envelope enclosing a mercury fill 2| and a displacement means generally designated 22, the displacement means being in the form of an armature for electromagnetic switch actuation. In the normal or deenergized state of the switch, the displacement means 22 is free to float with its lower end partially submerged in the mercury fill, as shown in Fig. 1. Energization of an exterior electromagnetic means generally designated 23 draws the displacement means 22 downward thereby raising the level of the mercury fill to bridge the electrodes. I

The electromagnetic means 23 may comprise a. coil 25 having an iron circuit 26 and providing an axial opening to receive and retain the switch envelope 20. In the particular construction shown in the drawings, the iron circuit includes two circular pole pieces 2'! defining an air gap 28 and the switch envelope 2|] is mounted in proper position relative to the air gap by a rubber collar 29 tightly embracing an insulating sleeve 30. The insulating sleeve 30, which may be Bakelite, completely surrounds the switch envelope 2|! and is suitably bonded thereto. Preferably a bracket 3 is adjustably mounted on the iron circuit 26 by machine screws 39 to engage the rubber collar 29, as shown.

The switch envelope 20 comprises a cylindrical wall 3|, an upper cap 32, and a lower cap 33. The cylindrical wall 3| is polished on its inner surface to minimize frictional resistance to movement of the displacement means 22 and is counterbored at its opposite ends to provide shoulders to seat the two caps 32 and 33. The cylindrical wall 3| of the envelope should be made of metal that is nonmagnetic and also resistant to wetting by mercury. A suitable metal, for example, is a stainless steel known as "18-8 Steel having besides iron, approximately 18% chromium and 8% nickel.

The upper cap 32 may be a metal disc or a pressed sheet metal member with an upturned flange 31 to nest inside of the cylindrical wall 3|.

The joint between the cap 32 and the cylindricalwall 3| of the envelope may be sealed in any suitable manner, for example, by welding as indicated at 38. The cap 32 has a central flanged aperture to embrace a body of insulating material 4| having the function of holding a switch electrode 42. The electrode 42 extends into the interior of the switch envelope 20 and at its outer end is adapted for connection with a wire 43 of the circuit to be controlled by the switch.

It is requisite that the materials of the cap 32, the insulating body 4| and the electrode 42 all have substantially the same coefficient of thermal expansion to maintain effective sealing relationships under varying temperature conditions. In my preferred embodiment of the invention, the electrode 42 is made of molybdenum, the insulating body 4|. is a hard glass such as Corning G 705 AJ fused both to the electrode and to the cap, and the cap 32 is fabricated from a metal known to the trade as Kovar, an alloy manufactured by Stupakoif Laboratories, Pittsburgh, Pennsylvania.

The second wire 45 of the circuit to be controlled by the switch may be soldered to the cap wall 3|, the cap being sealed by welding 41. The

cap 33, which may be machined from cold rolled steel has an axial bore 50 sealed by a headed pin or plug 5|. may be evacuated from the welded envelope through the bore 53 and then a suitable inert gas or mixture of inert gases may be introduced through the same bore to fill the envelope under pressure. The gas or gases may be selected from a group comprising hydrogen, nitrogen, argon, and helium. After the gas has been introduced to the desired pressure, the head of the pin or plug 5| is welded to seal the bore 50.

The present invention is directed to the method of mounting aquartz cup 52 on the end of the electrode 42. In preparation for assembling the quartz cup on the electrode 42, the electrode is cutaway, as indicated in Fig. 2, to provide a head portion 53 and a restricted neck 55. To mount the quartz cup 52 en the electrode 42, the headed end of the electrode is inserted into the cup, as shown in Fig. 2. Then heat is applied by suitable means such as an oxyacetylene flame to melt or soften the material of the cup sufiiciently to per- In the course of manufacture, air

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as best-shown in Fig. 3. Since the head portion 53 of the electrode 52 is larger in diameter than the restricted or collapsed portion-of the cup 52 embracing: the neck rportion:;5.5 zof that-electrode, the cup and electrode cannot beseparated'withe' out either breaking, or melting the material of one or the other. No great skill is required to collapse-the cup into permanent rigid engagement with the electrode.

Fig.4 illustrates the fact that a head-56 may beformed on an electrode 51 by enlargingthe end of the electrode rather than by cutting away a portion of the electrode. As indicated in Fig. 4, the headed electrode 51 is engaged with a quartz cup 58 in the manner above described.

Figs. 5 and 6 indicate how a quartz cup 60 may be mounted on a metal post, generally designated 6|, in position to hold a small body of mercury 62 immersing the lower end of an upper electrode 63. Since the post 6| is of conducting material and together with the switch envelope 20 forms a part of the circuit, the metal post may be termed a second or lower electrode. This lower electrode 6! may be attached to the switch envelope 20 in any suitable manner. For example. as shown in the drawings, the electrode 6| may include a rod-like member 65 threaded into a short metal sleeve 66, the sleeve in turn embracing a boss 6'! of a metal cap 68 constituting the lower end of the switch envelope. For evacuating the metal envelope in thecourse of manufacture, the sleeve 66 may have at least one aperture and the metal can 68 may have an axial bore ll extending through the boss 61, the bore being finally closed by a headed pin 12 and sealed by welding or soldering.

The upper end of the lower electrode 6| is formed with a head 13, as heretofore described, and the cup 68 is initially formed with a recess on its underside dimensioned to receive the headed electrode, the bottom wall of the cup being relatively thick to accommodate such a recess. In the process of fabrication, the cup 60 is backed onto the electrode 6 I, as shown in Fig. 5, and then an oxyacetylene flame is applied to the underside of the cup in such manner as to cause the quartz material of the cup to flow into rigid inseparable embracement of the electrode. material of the cup 60 is deformed in such manner as to cause the recess to contract into positive engagement with the electrode head 13. By forming the recess in the wall of the cup instead of forming an aperture through the cup wall, I avoid any possibility of a short-circuiting mercury path being formed through the wall of the cup.

The purpose of Figs. 7 and 8 is to illustrate the fact that a quartz cup 16 may be mounted on the electrode 6| in much the same manner as just described but Without preforming the cup with a bottom recess. The cup 16 in its initial form shown in Fig. 7 has a plain bottom of substantial thickness. The cup is backed against the end of the headed electrode, as indicated in Fig. 7, and then an oxyacetylene flame is played against the lower portion of the cup and the cup is manipulated in such manner as to cause the heat-softened quartz to be deformed into encasement of the electrode head, as shown in Fig. 8.

In the cup-mounting procedure illustrated by Figs. 9 and 10, a plain cylindrical recess 11 is formed in the upper end of a relatively thick lower electrode 18. A quartz cup 88 for mounting on such an electrode is formed with a down- In effect, the

wardly extendingportion "8 I that is, of headed aor flaring configuration. The fabrication procedure consists of backing the headed portion 8| of the formation of the'electrode end may be accom-x plished-byusing roller means to subject the end of the electrode to radial pressure.

In the mounting method illustrated by Figs. 11 and 12 the upper end of a relatively thick lowerelectrode 82 is provided-with a 'recess 83 that is undercut or enlarged so that the entrance to the recess is relatively restricted. The quartz cup 85 is initially formed with a downwardly extending cylindrical portion or stem 86 that fits into the recess entrance, as indicated in Fig. 11. It is contemplated that the cup 85 will be subjected to longitudinal pressure to urge the stem 86 of the cup against the bottom of the recess and that simultaneously the cup stem 86 will be subjected to sufiicient heat to cause the cylindrical portion to soften and deform by flowing action into a configuration occupying the recess 85 to such extent as to provide the desired rigid inseparable connection between the cup and the electrode. Thus Fig. 12 shows the cup 85 in its final i'orm having a portion encased by the material of the electrode 8'2, the encased portion being formed with a head 81.

Since the electrode '82 may be made of a metal having a melting point greatly exceeding the melting point of quartz, the heat-deformation of the cup stem 86 may be achieved by applying an oxyacetylene flame both to the end of the electrode and to the cup stem 86, heat being conducted to the quartz through the metal of the electrode. The required heat-deformation of the cup stem 86 may also be accomplished by heating the electrode end and the enclosed cup stem inductively by means of an electric coil, pressure being applied simultaneously to urge the cup stem towards the bottom of the recess.

The various cups mentioned above are described as made of quartz because quartz proves so satisfactory in switch service, quartz being immune to attack by mercury and being unaffected by the repeated breaking of high current circuits. The cups may be fabricated from any materials that have the properties required for service in a mercury switch and the properties necessary for carrying out the steps of the mounting process.

The various specific forms and practices of my invention set forth in detail herein for the purpose of disclosure suggest various substitutions and modifications under my concept and I reserve the right to all such departures from my description that properly come within the terms of my appended claims.

This is a division of application No. 550,340, filed August 21, 1944, now abandoned.

I claim:

1. In a mercury switch, a, switch envelope, a mercury n11, a quartz cup member in said envelope having imperforate Walls to hold a pool of mercury, and an electrode member in said envelope, one of said members having an integral head portion thereof inseparably encased by an integral portion of the other, said integral portion of the other member including a restricted neck portion collapsed over and overlying said head portion and forming a. mechanical interlock between the two members.

2. The combination as set forth in claim 1 in whichthe electrode member extends downwardly into the cup member-and has said integral head portion at the lower end thereof for encasement by the bottom portion of the cup member.

'-3..The combination set forth in claim -1 in which :the electrode member extends upwardly trode member extends u and encases said head portion.

EVERETT v. TORGESON. REFERENCES CITED pwardly in the envelope The'following references are of record in the file of this-patent: r

I UNITED STATES PATENTS 1 Number Name Date Zuckschwerdt June 27, 1933 Larson Sept. 4, 1945 Larson June 11, 1946 

